WO2017219853A1

WO2017219853A1 - Single-walled carbon nanotube flexible transparent conductive thin film with carbon welded structure and preparation method therefor

Info

Publication number: WO2017219853A1
Application number: PCT/CN2017/087254
Authority: WO
Inventors: 侯鹏翔; 蒋松; 刘畅; 成会明
Original assignee: 中国科学院金属研究所
Priority date: 2016-06-22
Filing date: 2017-06-06
Publication date: 2017-12-28
Also published as: US20190256356A1; CN107527673B; CN107527673A; EP3477663A1; JP6845259B2; JP2019521943A; EP3477663A4

Abstract

A single-walled carbon nanotube flexible transparent conductive thin film with a carbon welded structure and a preparation method therefor. In the process of growing a single-walled carbon nanotube by means of floating catalyst chemical vapor deposition, the concentrations of a catalyst and a carbon source and the residence time thereof in the constant temperature region are reduced, so that part of the carbon source decomposed by means of the catalyst forms an sp² carbon island which is welded at the intersection of individual single - walled carbon nanotubes, and finally, a single-walled carbon nanotube thin film with an sp² carbon island welded structure is formed. The thin film of the structure has better photoelectric properties, chemical stability and flexibility than the ITO thin film on a flexible substrate. The contact resistance between carbon nanotubes is reduced, the formation of tube bundles and a large absorption of light are inhibited, and a high-performance flexible transparent conductive thin film is obtained by designing and preparing the individual carbon nanotubes bonded by means of a carbon welded structure. The high-performance flexible transparent conductive thin film is of great significance for promoting the application of a carbon nanotube thin film in the field of high-performance optoelectronic devices.

Description

Carbon-welded single-walled carbon nanotube flexible transparent conductive film and preparation method thereof

Technical field

The invention relates to the field of preparation of high-performance flexible transparent conductive film, in particular to a carbon-welded single-walled carbon nanotube flexible transparent conductive film and a preparation method thereof.

Background technique

The transparent conductive film is an important component of electronic devices such as touch screens, flat panel displays, photovoltaic cells, and organic light emitting diodes. At present, indium tin oxide (ITO) is the most mature transparent conductive film for commercial applications, but the decreasing cost of rare metal indium makes the cost of ITO gradually increase. On the other hand, with the rise of flexible electronics, the brittleness of ITO cannot meet the future application. demand. Due to its good optoelectronic properties, structural stability, flexibility and other characteristics, the two-dimensional network transparent conductive film interwoven with single-walled carbon nanotubes is expected to replace resource scarcity and brittleness due to its high transparent conductivity and excellent flexibility. Indium tin oxide has become a new generation of transparent conductive films and has been widely used.

At present, there are mainly two methods for preparing a single-walled carbon nanotube flexible transparent conductive film. One is a wet method (solution method), in which a single-walled carbon nanotube is first dispersed in a solution, and then a single-walled carbon nanotube is deposited on a flexible substrate by filtration, spraying, suspension coating or printing. The limitation of this method is that the physical and chemical processes of dispersing single-walled carbon nanotubes can destroy the intrinsic structure of the carbon nanotubes, introduce pollutants such as surfactants, and thereby reduce the performance of the obtained transparent conductive film. The other is a dry method in which a collecting device is installed at the end of the reaction system for growing single-walled carbon nanotubes, and the grown single-walled carbon nanotubes are directly collected on the porous substrate; and the carbon nanotubes are transferred to the embossing process. A transparent conductive film is formed on a flexible substrate (Document 1, Kaskela A, Nasibulin A G, Timmermans M Y, et al. Aerosol-synthesized SWCNT networks with tunable conductivity and transparency by a dry transfer technique [J]. Nano letters, 2010, 10 (11): 4349-4355.); The method has the advantages of maintaining the intrinsic structure of the carbon nanotubes and not introducing pollution, and is low in consumption, simple, and easy to scale production. Therefore, a series of advances have been made in the dry preparation of carbon nanotube transparent conductive films, such as reducing tube bundle size, reducing contact resistance, patterning, etc. (2, Mustonen K, Laiho P, Kaskela A, et al. Uncovering) The ultimate performance of single-walled carbon nanotube films as transparent conductors [J].Applied Physics Letters, 2015, 107(14): 143113. Document 3, Fukaya N, Kim D Y, Kishimoto S, et al. One-step sub -10 μm patterning of carbon-nanotube thin films for transparent conductor applications [J]. ACS nano, 2014, 8(4): 3285-3293.).

It has been reported that the photoelectric properties of single-walled carbon nanotube transparent conductive films obtained by dry transfer (sheet resistance greater than 200 Ω/□ (ohm/sq) @90% transmittance) cannot be compared with ITO (less than 50 Ω/□@90% light transmission) The rate is comparable and far below the predicted value of single-walled carbon nanotubes. This is mainly because the commonly produced single-walled carbon nanotubes are aggregated into bundles of ten to several tens of nanometers in diameter due to the strong van der Waals force between the tubes, and the single-walled carbon nanotubes in the bundle do not contribute to the conductivity of the film but absorb. A large amount of light, thus reducing the photoelectric properties of the film (Document 4,

M, Lefebvre J, Johnson A T. High-field electrical transport and breakdown in bundles of single-wall carbon nanotubes [J]. Physical Review B, 2001, 64(24): 241307.). Kauppinen et al. reduced the yield of carbon nanotubes by reducing the amount of catalyst supply, and obtained single-walled carbon nanotubes with a single root ratio of more than 50%. The preferred photoelectric properties of the prepared transparent conductive film were 310 Ω/□@90% transmittance ( Document 2, Mustonen K, Laiho P, Kaskela A, et al. Uncovering the ultimate performance of single-walled carbon nanotube films as transparent conductors [J]. Applied Physics Letters, 2015, 107(14): 143113.). On the other hand, due to the nanometer size of single-walled carbon nanotubes, the contact resistance between the tubes is considered to be a major contributor to the sheet resistance. Researchers usually use nitric acid doping to reduce the contact resistance between carbon nanotubes (Document 5, Jackson R, Domercq B, Jain R, et al. Stability of doped transparent carbon nanotube electrodes [J]. Advanced Functional Materials, 2008 , 18(17): 2548-2554.). However, this chemical doping effect is not stable, resulting in a gradual rise in sheet resistance.

Summary of the invention

The object of the invention is a carbon-welded single-walled carbon nanotube flexible transparent conductive film and a preparation method thereof, which solve the key problems of large-band absorption of light and reduction of contact resistance between tubes by single-walled carbon nanotubes, and obtain performance. A single-walled carbon nanotube flexible transparent conductive film comparable to flexible ITO and having high stability.

The technical solution of the present invention is:

A carbon-welded single-walled carbon nanotube flexible transparent conductive film designed and coated with a highly crystalline graphene sp ² carbon island at a single-walled carbon nanotube overlap, and a graphene sp ² carbon island welded to a single single wall A single-walled carbon nanotube film having a sp ² carbon island welded structure is formed at an intersection between the carbon nanotubes; in a single-walled carbon nanotube network, the ratio of the single carbon nanotubes is 80 to 88%, and the single structure is carbon-welded The pipe joints of the carbon nanotubes are tightly connected.

The carbon-welded single-walled carbon nanotube flexible transparent conductive film, the graphene carbon island and the single-walled carbon nanotube in the carbon welded structure have a crystallinity I _G /I _D of 150 to 180, and the sp ² CC bond ratio It is 97 to 99%, and the antioxidant temperature exceeds 750 to 800 °C.

The carbon-welded single-walled carbon nanotube flexible transparent conductive film has a length of 10 to 200 μm and a diameter of 1.4 to 2.4 nm.

The carbon steel structure single-walled carbon nanotube flexible transparent conductive film is prepared by using a volatile metal organic compound ferrocene as a catalyst precursor, a sulfur-containing organic compound thiophene as a growth promoter, hydrocarbon ethylene and toluene For the carbon source and hydrogen as the carrier gas, the carbon nanotubes are grown at 1100 ° C in the reaction furnace, and the high-quality single-walled carbon nanotube flexible transparent conductive film is collected in situ at the end of the furnace tube of the reaction furnace.

The method for preparing the carbon-shielded single-walled carbon nanotube flexible transparent conductive film, the specific steps are as follows:

(1) Under the protection of argon, first raise the temperature of the reactor to 1100±50 °C, and then pass the carrier gas hydrogen and the main carbon source ethylene;

(2) Under carrier gas carrying, the solution supplied by the syringe pump contains auxiliary carbon source toluene, catalyst precursor ferrocene and growth promoter thiophene volatilized into the high temperature region of 1100±50 °C; ferrocene and thiophene are cleaved to form catalyst particles, Ethylene and toluene cleave carbon atoms under the catalytic action of the catalyst, and nucleate and grow single-walled carbon nanotubes on the catalyst particles;

(3) The carbon nanotubes flow along the gas flow to the tail end of the furnace tube, and finally are filtered by the porous filter membrane disposed at the tail end to form a macroscopic two-dimensional carbon nanotube film.

The method for preparing a carbon-shielded single-walled carbon nanotube flexible transparent conductive film, in the process of growing single-walled carbon nanotubes by floating catalyst chemical vapor deposition, by reducing the concentration of the catalyst and the carbon source and the residence time in the constant temperature zone So that a part of the carbon source decomposed by the catalyst forms a sp ² carbon island, welded at the intersection between the single single-walled carbon nanotubes, and finally forms a single-walled carbon nanotube film having a sp ² carbon island welded structure; argon before and after preparation The gas flow rate is 180-220 ml/min, the hydrogen flow rate in the preparation is 4500-8000 ml/min, the ethylene flow rate is 2-20 ml/min, the solution supply rate is 0.1-0.24 ml/hr, and the solution formulation is toluene: Ferrocene: thiophene = 10 g: (0.05 to 0.6) g: (0.025 to 0.9) g.

The carbon-welded single-walled carbon nanotube flexible transparent conductive film is transferred to a flexible substrate by an imprint method to construct a flexible transparent conductive film.

The carbon welded structure single-walled carbon nanotube flexible transparent conductive film, the flexible substrate is polyethylene terephthalate, polyethylene naphthalate or polycarbonate.

The carbon-welded single-walled carbon nanotube flexible transparent conductive film and the single-walled carbon nanotube flexible transparent conductive film have excellent uniformity: the transmittance error is ±0.4%, and the sheet resistance error is ±4.3%.

The design idea of the invention is:

The invention utilizes the difference in decomposition temperature between the gas phase carbon source and the liquid phase carbon source to realize the decomposition of the carbon source in the middle-high temperature to high temperature range in the reaction system, thereby inhibiting the catalyst particles from agglomerating or excessively adsorbing carbon and poisoning; selecting extremely low carbon Source and catalyst concentration to reduce the number of nucleation of carbon nanotubes, thereby reducing the chance of contact between the carbon nanotubes to form a tube bundle; selecting a high carrier gas flow rate to reduce the residence time of the catalyst and carbon source in the growth zone, so that some carbon atoms cannot Timely participation in the growth of carbon nanotubes to form highly crystalline graphene carbon islands. Under the combined action of thermal motion and van der Waals force, some graphene carbon islands are adsorbed on the surface of the carbon nanotubes, thereby suppressing the formation of tube bundles. Due to the filtration of the porous membrane, the carbon nanotubes are deposited and overlap each other on the surface of the membrane. As the reaction progresses, the graphene carbon islands in the gas stream are deposited at the junction between the tube and the tube, eventually forming a graphene island welded structure. In the high-performance flexible single-walled carbon nanotube film welded by graphene island, one of the functions of the graphene island welding structure is to reduce the contact resistance between the carbon nanotubes, and the second effect is to suppress the aggregation between the tubes. The problem of massive absorption of light.

The advantages and benefits of the present invention are:

1. The present invention designs and prepares a carbon-welded single-walled carbon nanotube flexible transparent conductive film for the first time, which effectively solves the problem of large contact resistance between tubes in a single-walled carbon nanotube film and a large amount of light absorption by the tube bundle.

2. The carbon-welded single-walled carbon nanotube flexible transparent conductive film obtained by the invention has a sheet resistance of only 41 Ω/□ at 90% transmittance (550 nm visible light); at the same transmittance, the sheet resistance ratio is currently reported. The undoped carbon nanotube transparent conductive film has a minimum sheet resistance of 5.5 times lower; and is at the same level as the optimum performance of the flexible substrate ITO transparent conductive film.

3. The flexible transparent conductive film technology for preparing carbon-welded single-walled carbon nanotubes developed by the invention has the characteristics of simple process and easy scale, thereby solving the key science and technology of poor stability and complicated process of carbon nanotube transparent conductive film. The problem is expected to play an important role in the fields of touch screen, liquid crystal display, and organic light-emitting display.

4. In the process of growing single-walled carbon nanotubes by floating catalyst chemical vapor deposition method, the carbon source which is partially decomposed by the catalyst forms a sp ² carbon island by reducing the concentration of the catalyst, the carbon source and the residence time in the constant temperature zone. Soldering at the intersection between single single-walled carbon nanotubes, finally forming a sp ² carbon island welded high-performance single-walled carbon nanotube flexible transparent conductive film.

5. The invention provides a high-performance flexible transparent conductive film by designing and preparing a single carbon nanotube bonded by a carbon welded structure, reducing the contact resistance between the carbon nanotubes, suppressing tube bundle formation and mass absorption of light, and obtaining a high-performance flexible transparent conductive film. The application of carbon nanotube film in the field of high performance optoelectronic devices is of great significance.

DRAWINGS

Figure 1. Single wall carbon nanotube film preparation system. In the figure, 1 reaction furnace; 2 precision injection pump; 3 temperature controller.

Figure 2. SEM characterization of the ## sample. (a)-(b) are high- and low-magnification SEM images of the sample, respectively; (c) is a statistical diagram of the length of the carbon nanotubes in the sample.

Figure 3. TEM, Raman spectroscopy, XPS, and heat treatment characterization results for the ## sample. (a) is a low- and high-power transmission electron micrograph of the sample; (b) is a statistical graph of the number of individual carbon nanotubes contained in a single bundle of the sample; (c) is a transmission electron microscope diameter of the carbon nanotube in the sample (d) is the Raman spectrum G-mode and D-mode diagram of the sample; (e) is the X-ray photoelectron spectroscopy of the sample; (f) is a transmission electron micrograph of the air heat treatment at 700 ° C for 30 minutes.

Figure 4. Results of the uniformity of the 1# sample. (a) is an optical photograph of a carbon nanotube transparent conductive film of a marker sheet resistance and light transmittance transferred to a transparent flexible substrate; (b) is a schematic diagram of the uniformity of the diagram (a).

Figure 5. Results of the performance stability test for the #1 sample. (a) Performance stability map of carbon nanotube film doped with or without nitric acid in air; (b) repeated bending test of single-walled carbon nanotube film and commercial ITO (base PET) (bending angle of 70°) The results are compared; (c) is a comparison of the results of a single large angle bending test (bending angle of 180°) of the original sample and commercial ITO (base PET).

Figure 6. TEM photograph of the 2# sample. (a)-(b) are low- and high-power TEM photographs of the samples, respectively.

detailed description

As shown in FIG. 1 , the single-walled carbon nanotube film preparation system mainly comprises a reaction furnace 1, a precision injection pump 2, a temperature controller 3, etc., the reaction furnace 1 is connected with a precision injection pump 2, and the precision injection pump 2 will be raw material toluene, two. The ferrocene and thiophene are injected into the reaction furnace 1, and a mixed gas of hydrogen and ethylene is introduced into the reaction furnace 1 through a pipeline, and a temperature controller 3 is disposed outside the pipeline.

In the specific implementation process, the invention adopts the injection floating catalyst CVD method to control the preparation of the carbon-welded single-walled carbon nanotube flexible transparent conductive film, and the volatile metal organic compound ferrocene as the catalyst precursor and the sulfur-containing organic compound thiophene Growth promoter, hydrocarbon ethylene and toluene are carbon sources, hydrogen is carrier gas, carbon nanotubes are grown at 1100 ° C and high-quality single-walled carbon nanotube flexible transparent conductive film is collected in situ at the end of the furnace tube. as follows:

(1) Under the protection of argon, first raise the temperature of the reactor to 1100 ° C, and then pass the carrier gas hydrogen and the main carbon source ethylene;

(2) Under carrier gas carrying, the solution supplied by the syringe pump (including auxiliary carbon source toluene, catalyst precursor ferrocene and growth promoter thiophene) rapidly volatilizes into the high temperature zone (1100 ° C); ferrocene and thiophene are cleaved to form Catalyst particles, under the catalytic action of the catalyst, ethylene and toluene cleave carbon atoms and nucleate and grow single-walled carbon nanotubes on the catalyst particles;

(3) The carbon nanotubes flow along the gas flow to the end of the furnace tube, and finally are filtered by the porous membrane placed at the tail end to form a macroscopic two-dimensional carbon nanotube film, thereby realizing the in-situ gas phase collection of the carbon nanotube film on the porous substrate; The resulting film thickness is different.

(4) At the end of the preparation, the reaction furnace and the temperature controller start to cool down, the injection pump stops working, the hydrogen and ethylene are stopped, and the argon gas is introduced to discharge the gas in the reaction tube.

Wherein, the flow rate of argon gas before and after preparation is 200 ml/min, the flow rate of hydrogen in preparation is 4500-8000 ml/min, the flow rate of ethylene is 2-20 ml/min, and the supply rate of the solution is 0.1-0.24 ml/hr. The solution formulation was toluene: ferrocene: thiophene = 10 g: (0.05 - 0.6) g: (0.025 - 0.9) g.

The high-performance single-walled carbon nanotube flexible transparent conductive film obtained by the invention designs and coats a highly crystalline graphene carbon island at a single-walled carbon nanotube lap joint, and the carbon island structure solves the single wall due to van der Waals force The problem that the carbon nanotubes are aggregated into a large amount of light absorption and the contact resistance between the carbon nanotubes is large, and finally a high-performance flexible transparent single-walled carbon nanotube conductive film is obtained. The proportion of single carbon nanotubes in a single-walled carbon nanotube network is as high as 85%, which avoids the large absorption of light by a tube bundle (usually a bundle size of several tens of nanometers) in a conventional single-walled carbon nanotube network. A problem that does not contribute to conductivity. The carbon welded structure tightly connects the overlapping portions of the carbon tubes, which greatly reduces the contact resistance between the tubes, and solves the problem of reducing the splicing resistance of the carbon nanotubes. The carbon islands and single-walled carbon nanotubes in the carbon-welded structure have very high crystallinity (I _G /I _D is 175, sp ² CC bond ratio is 98.8%, oxidation temperature exceeds 700 ° C), and the length of carbon nanotubes is long. (10 to 200 μm) and large diameter (1.4 to 2.4 nm). The porous substrate is installed at the end of the furnace tube to collect the carbon nanotube film in situ, which not only eliminates the complicated solution, but also dissolves the film formation process and introduces impurities, and ensures the integrity of the intrinsic structure of the carbon nanotube.

The invention can transfer the carbon nanotube film to the flexible substrate by simple imprinting method (for example, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polycarbonate Ester (PC), etc.) A flexible transparent conductive film having a sheet resistance of only 41 Ω/□ at 90% transmittance (550 nm visible light) was constructed. At the same transmittance, the sheet resistance of the undoped original carbon nanotube transparent conductive film is 5.5 times lower than the lowest reported value of the current pure carbon nanotube transparent conductive film, reaching the level of the commercial ITO flexible film. The obtained single-walled carbon nanotube film has excellent uniformity (light transmittance error of ±0.4%, sheet resistance error of ±4.3%), air stability, high temperature and high humidity stability, and repeated bending and single large It still shows good performance stability after the angle bending test.

Among the products obtained by the method of the present invention, the high-performance characterization techniques for evaluating the single-walled carbon nanotube transparent conductive film are: photoelectric performance test, air stability test, accelerated aging test, repeated bending test and single bending test.

The invention will be described in detail below by way of examples and the accompanying drawings.

Example 1

In this embodiment, under the protection of argon gas of 200 ml/min, the temperature of the reactor is first raised to 1,100 ° C, and then hydrogen gas, carbon source, catalyst precursor ferrocene, growth promoter thiophene are introduced into 8060 ml/min. . Wherein, the volume concentration of ethylene in the gas phase carbon source is 1.4×10 ^-3 in the reaction system, the volume concentration of toluene in the reaction system is 6.1×10 ^-3 , and the volume concentration of the catalyst precursor ferrocene in the reaction system is 1.5×10 ^{− 6.} The volume concentration of the growth promoter thiophene in the reaction system is 5×10 ^-7 . The grown carbon nanotubes flow to the end of the furnace tube with the gas stream, and finally form a macroscopic two-dimensional carbon nanotube film on the porous filter film placed at the tail end. By controlling the collection time, films of different light transmittances can be obtained.

The single-walled carbon nanotube film sample prepared as described above (denoted as #1) was characterized by transmission electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, sheet resistance, light transmittance, etc., and subjected to high temperature heat treatment and air. Stability, accelerated aging, repeated bending and single large angle bending tests.

Scanning electron microscopy (Fig. 2) revealed that the carbon nanotubes were long and straight, with an average length of 62 μm. Transmission electron micrograph (Fig. 3) shows that the carbon nanotubes in the film are covered with graphene islands, forming a single-walled carbon nanotube network structure welded by graphene islands; 85% of single-walled carbon nanotubes are single Roots, the other 15% are two or three small tube bundles, no more tube bundles are found; single-walled carbon nanotubes have a diameter of 1.4 to 2.4 nm (Fig. 3). The Raman spectrum of the single-walled carbon nanotube film (Fig. 3) has a very high-intensity G-mode and a very low-intensity D-mode (I _G /I _D is 175, usually reported in the literature as I _G /I _{D is} less than 50), It is indicated that the single-walled carbon nanotubes and graphene islands in the film have very high crystallinity; at the same time, the X-ray photoelectron spectroscopy (Fig. 3) shows that the sp ² CC structure ratio is 98.8%, which also proves the high crystallinity of the film. The carbon-welded structure film was oxidized in air at 700 ° C for half an hour and then subjected to transmission electron microscopy. The results (Fig. 3) showed that the carbon-welded structure and the single-walled carbon nanotube structure showed almost no change, which further proved that the obtained film was obtained. The film has high crystallinity.

The collected carbon-welded single-walled carbon nanotube film was transferred onto a flexible PET substrate by imprinting, and the film sheet resistance of 90% transmittance (550 nm visible light) was measured to be only 41 Ω/□; and the film had excellent uniformity. The uniformity of the film having a size of 8 × 8 cm ² was tested (Fig. 4), the film transmittance error was ±0.4%, and the sheet resistance error was ±4.3%. The film also has good stability. After being placed in air for more than 60 days, the sheet resistance value changes by less than 2% (Fig. 5), which is in sharp contrast with the film doped with nitric acid; after 250 hours of accelerated aging test The sheet resistance value changes less than 5% (Table 1); after 10,000 70° bending experiments or a single 0-180° bending test, the sheet resistance change is less than 15% (Fig. 5), and the ITO properties on the flexible substrate are formed. sharp contrast.

Table 1. Accelerated aging test results for 1# samples (test conditions are 250 hours @60°C & 90% relative humidity)

Test conditions: 250h@60°C & 90% relative humidity.

Example 2

In this embodiment, under the protection of argon gas of 200 ml/min, the temperature of the reactor is first raised to 1100 ° C, and then 6530 ml / min of hydrogen, carbon source, catalyst precursor ferrocene, growth promoter thiophene are introduced. . Wherein, the volume concentration of ethylene in the gas phase carbon source is 2.4×10 ^-3 in the reaction system; the volume concentration of toluene in the reaction system is 4.4×10 ^-3 , and the volume concentration of the catalyst precursor ferrocene in the reaction system is 1.1×10 ^{− 6.} The volume concentration of the growth promoter thiophene in the reaction system is 3.7×10 ^-7 . The grown carbon nanotubes flow to the end of the furnace tube with the gas stream, and finally deposit a macroscopic two-dimensional carbon nanotube film on the porous filter film disposed at the tail end. By controlling the collection time, films of different light transmittances can be obtained.

The single-walled carbon nanotube film samples prepared above were characterized by transmission electron microscopy, sheet resistance and light transmittance. Transmission electron microscopy (TEM) characterization showed that the carbon nanotubes in the film were coated with graphene islands, forming a single-walled carbon nanotube network structure welded by graphene islands. The collected carbon-welded single-walled carbon nanotube film was transferred onto a flexible PET substrate by imprinting, and the film sheet resistance of 90% transmittance (550 nm visible light) was measured to be 50 Ω/□.

Comparative example

Under the protection of 200 ml/min argon, the temperature of the reactor was raised to 1100 ° C, and then 4,560 ml / min of hydrogen, carbon source, catalyst precursor ferrocene, growth promoter thiophene, and gas phase carbon source were introduced. The volume concentration of ethylene in the reaction system is 2.4×10 ^-3 , the volume concentration of toluene in the reaction system is 1.1×10 ^-2 , and the volume concentration of the catalyst precursor ferrocene in the reaction system is 2.7×10 ^-6 , growth promoter The volume concentration of thiophene in the reaction system was 8.9×10 ^-7 . The grown carbon nanotubes flow to the end of the furnace tube with the gas stream, and finally form a macroscopic two-dimensional carbon nanotube film on the porous filter film placed at the tail end. By controlling the collection time, films of different light transmittances can be obtained.

The single-walled carbon nanotube film samples prepared above (denoted as #2) were characterized by transmission electron microscopy, sheet resistance, and light transmittance. The transmission electron micrograph is shown in Fig. 6. It can be seen that the sample is composed of a bundle of 5 nm to 40 nm, and there is no carbon welded structure between the bundles. The collected single-walled carbon nanotube film was transferred onto a flexible PET substrate by embossing, and the film sheet resistance of 90% transmittance (550 nm visible light) was measured to be 270 Ω/□.

The results of the examples and the comparative examples show that the graphene island welded high performance single-walled carbon nanotube network film designed and prepared by the invention has high quality, high single root rate, long length and large diameter, so that the single-walled carbon nanotubes have high quality. The prepared transparent conductive film reaches the best reported level of ITO film on the flexible substrate for the first time, which is 5.5 times of the best performance of the currently reported carbon nanotube film without any treatment. The transparent conductive film also has good chemical stability and Flexible. The invention realizes the preparation of the high-performance single-walled carbon nanotube transparent conductive film, and solves the key scientific and technical problems such as poor photoelectric performance and complicated process of the carbon nanotube transparent conductive film.

Claims

A carbon-welded single-walled carbon nanotube flexible transparent conductive film characterized in that a high-crystalline graphene sp 2 carbon island is designed and coated at a single-walled carbon nanotube overlap, and a graphene sp 2 carbon island is welded The intersection of single single-walled carbon nanotubes forms a single-walled carbon nanotube film with sp 2 carbon island welded structure; in a single-walled carbon nanotube network, the ratio of single carbon nanotubes is 80-88%, through carbon The welded structure tightly connects the pipe joints of the single carbon nanotubes.
The carbon-shielded single-walled carbon nanotube flexible transparent conductive film according to claim 1, wherein the graphene carbon island and the single-walled carbon nanotube in the carbon-welded structure have a crystallinity I G /I D of 150 ～ The 180, sp 2 CC bond ratio is 97 to 99%, and the oxidation resistance temperature exceeds 750 to 800 ° C.
The carbon-welded single-walled carbon nanotube flexible transparent conductive film according to claim 1, wherein the single-walled carbon nanotube has a length of 10 to 200 μm and a diameter of 1.4 to 2.4 nm.
A method for preparing a carbon-welded single-walled carbon nanotube flexible transparent conductive film according to claim 1, characterized in that the volatile metal organic compound ferrocene is used as a catalyst precursor and the sulfur-containing organic compound thiophene is grown. Promoter, hydrocarbon ethylene and toluene are carbon sources, hydrogen is carrier gas, carbon nanotubes are grown at 1100 ° C in the reactor, and high-quality single-walled carbon nanotubes are collected in situ at the end of the furnace tube of the reactor. Conductive film.
The method for preparing a carbon-welded single-walled carbon nanotube flexible transparent conductive film according to claim 4, wherein the specific steps are as follows:

(1) Under the protection of argon, first raise the temperature of the reactor to 1100±50 °C, and then pass the carrier gas hydrogen and the main carbon source ethylene;

(2) Under carrier gas carrying, the solution supplied by the syringe pump contains auxiliary carbon source toluene, catalyst precursor ferrocene and growth promoter thiophene volatilized into the high temperature region of 1100±50 °C; ferrocene and thiophene are cleaved to form catalyst particles, Ethylene and toluene cleave carbon atoms under the catalytic action of the catalyst, and nucleate and grow single-walled carbon nanotubes on the catalyst particles;

(3) The carbon nanotubes flow along the gas flow to the tail end of the furnace tube, and finally are filtered by the porous filter membrane disposed at the tail end to form a macroscopic two-dimensional carbon nanotube film.
The method for preparing a carbon-welded single-walled carbon nanotube flexible transparent conductive film according to claim 5, wherein the catalyst and the carbon source are reduced during the growth of the single-walled carbon nanotube by the floating catalyst chemical vapor deposition method Concentration and residence time in the constant temperature zone, the carbon source partially decomposed by the catalyst forms sp 2 carbon island, welded at the intersection between single single-walled carbon nanotubes, and finally forms a single-wall carbon with sp 2 carbon island welded structure. Nanotube film; the flow rate of argon gas before and after preparation is 180-220 ml/min, the flow rate of hydrogen in preparation is 4500-8000 ml/min, the flow rate of ethylene is 2-20 ml/min, and the supply rate of solution is 0.1-0.24 ml. /hour, the solution formulation is toluene: ferrocene: thiophene = 10 g: (0.05 - 0.6) g: (0.025 - 0.9) g.
The carbon-shielded single-walled carbon nanotube flexible transparent conductive film according to claim 5, wherein the carbon nanotube film is transferred onto the flexible substrate by an imprint method to construct a flexible transparent conductive film.
The carbon-welded single-walled carbon nanotube flexible transparent conductive film according to claim 7, wherein the flexible substrate is polyethylene terephthalate, polyethylene naphthalate or polycarbonate.
The carbon-shielded single-walled carbon nanotube flexible transparent conductive film according to claim 4 or 5, wherein the single-walled carbon nanotube flexible transparent conductive film has excellent uniformity: a transmittance error of ±0.4%, The sheet resistance error is ±4.3%.